The action movie star's beloved character, Rocky Balboa, has stood the the test of time, becoming a pop culture icon thanks to seven films over the course of four decades.

In honor of the hard-hitting, Philadelphia pugilist's big anniversary, here are 20 awesome facts you might not have known about the Rocky franchise.

Rocky was filmed in 28 days for a budget of just over than $1 million. It grossed $225 million at the box office.

The Rocky franchise has earned close to $1.5 billion at the box office throughout the years.

The famous "Rocky Steps" at the entrance to the Philadelphia Museum of Art contains exactly 72 stone steps.

"Gonna Fly Now," otherwise known as the Rocky theme song, reached No. 1 on the US Billboard Hot 100 charts in 1977.

Stallone says the hardest person to hit him on the set of a Rocky movie was former #WWE star Hulk Hogan. "We didn't put it in the movie because I was so traumatized," Stallone once said in an interview with Hogan.

The first film was nominated for nine Academy Awards, winning three Oscars for Best Picture, Best Director, and Best Film Editing.

After being nominated for Best Actor in Rocky, Stallone earned another Oscar nomination for Balboa in 2016. He was nominated in the Best Supporting Actor category for Creed, a role which also earned Stallone his first Golden Globe award.

Susan Sarandon auditioned to play Balboa's love interest of Adrian Pennino. However, the part ended up going to actress Talia Shire.

Stallone improvised Balboa's famous monologue where he turns down Mickey's offer to manage him.

Boxer Ken Norton was reportedly up for the role of Apollo Creed.

The character of Rocky Balboa was allegedly inspired by New York boxer Chuck Wepner, although Stallone initially denied it. The matter was settled after Wepner brought a lawsuit against the actor.

A writer once calculated that Balboa ran more than 30 miles between all of his jogging scenes in Rocky II, nearly the length of a 50k marathon.

Prior to becoming a TV star and landing the role of Clubber Lang, Mr. T worked as a bodyguard for boxing legends Muhammad Ali and Sugar Ray Leonard.

Butkus the dog was Stallone's real life companion during his early, struggling years. The actor was forced to sell his pet due to financial issues, but was reunited with the pup when he finally had enough money while filming Rocky.

Stallone penned the screenplay for each of the Rocky films except for Creed, which was written by director Ryan Coogler and Aaron Covington.

Stallone wrote the first movie in less than four days.

Elvis Presley called Stallone to have a screening of Rocky, but the actor was too scared to meet the rock star. "I was shy, believe it or not," he told GQ in 2010. "When he died in '77, I was doing F.I.S.T. So now I try to instill in my children: Grab something when it's offered. I'm not a big believer in reincarnation. I haven't met anyone yet: 'Look at me, I was a caterpillar!'"